Process for making filter tow

Abstract

A process for making a crimped tow of filaments suitable for forming a bale of crimped tow for conversion to cigarette filter rods comprising, presenting an uncrimped tow of filaments in a banded condition, adhesively bonding to the filaments of the banded tow ( 3 ), porous particles having absorbent surfaces imparting filtration capacity for tobacco smoke constituents, and crimping the banded tow, wherein the process comprises the steps, of: (i) pre-treating the particles to load them with a material capable of generating a gaseous emission from the particles thus forming pre-treated particles; (ii) applying to the filaments of the banded tow, the pre-treated particles and an adhesive for bonding the particles to the filaments; and subsequently (iii) treating the tow to generate the gaseous emission from the pre-treated particles so as to limit deactivation of the absorbent particle surfaces by the adhesive.

1. A process for making a crimped tow of filaments suitable for forming a bale of crimped tow for conversion to cigarette filter rods comprising, presenting an uncrimped tow of filaments in a banded condition, adhesively bonding to the filaments of the banded tow, porous particles having adsorbent surfaces imparting filtration capacity for tobacco smoke constituents, and crimping the banded tow, wherein the process comprises the steps of:
 (i) initially pre-treating the porous particles to load them with a material capable of generating a gaseous emission from the porous particles thus forming pre-treated particles; then 
 (ii) applying to the filaments of the banded tow, the pre-treated particles and an adhesive for bonding the particles to the filaments; and subsequently 
 (iii) treating the tow to generate the gaseous emission from the pre-treated particles so as to limit deactivation of the adsorbent particle surfaces by the adhesive; 
 wherein the absorbent surface area of the porous particles is at least 100 m 2 g −1 , and the mean particle diameter of the pre-treated particles is in the range of 1 to 20 microns. 
 
     
     
       2. A process according to  claim 1 , wherein the step of pre-treating the porous particles has a duration of between 12 to about 24 hours. 
     
     
       3. A process according to  claim 2 , characterised in that the material capable of generating a gaseous emission from the porous particles is a liquid which can be volatilized to generate a gas or a vapour by the action of heat and/or reduced pressure. 
     
     
       4. A process according to  claim 3 , characterised in that the material capable of generating a gaseous emission from the porous particles is water which can be volatilized to generate steam. 
     
     
       5. A process according to  claim 3 , characterised in that the porous particles are steeped in water as the pre-treatment for loading them with water. 
     
     
       6. A process according to  claim 5 , characterised in that the pre-treated particles and the adhesive are applied to the banded tow at the same time. 
     
     
       7. A process according to  claim 6 , characterised in that the pre-treated particles and the adhesive are pre-mixed before application to form a dispersion of the pre-treated particles in the adhesive. 
     
     
       8. A process according to  claim 7 , characterised in that the filaments of the tow have a cross-section having concave portions in which the adhered particles may lie. 
     
     
       9. A process according to  claim 7 , characterised in that the filaments have a cross-section which is a multi-lobal shape. 
     
     
       10. A process according to  claim 7 , characterised in that the filaments of the tow are cellulose acetate filaments. 
     
     
       11. A process according to  claim 7 , characterised in that the dispersion of the pre-treated particles in the adhesive is applied to the banded tow by passing a face of the banded tow over a surface onto which the dispersion is flowed. 
     
     
       12. A process according to  claim 11 , characterised in that the surface comprises an exterior surface of a tubular body and an interior portion, the tubular body being penetrated by a pattern of holes through which the dispersion is flowed from the interior of the tubular body to said exterior surface. 
     
     
       13. A process according to  claim 12 , characterised in that the banded tow is crimped directly after application of the pre-treated particles and the adhesive before the adhesive is dried and cured. 
     
     
       14. A process according to  claim 13 , characterised in that the banded tow is treated to generate the gaseous emission from the pre-treated particles directly after the crimping step. 
     
     
       15. A process according to  claim 14 , characterised in that the crimped banded tow is given a heat treatment both to generate the gaseous emission from the particles and to dry and cure the adhesive. 
     
     
       16. A process according to  claim 15 , characterised in that, after drying and curing of the adhesive, the banded tow is given a stretching treatment in order to effect a degree of breakage of inter-filament bonds caused by the adhesive. 
     
     
       17. A process according to  claim 7 , characterised in that the pre-treated particles comprise activated carbon, silica gel, a zeolite, an ion-exchange rein, or a clay, or a mixture of any of them. 
     
     
       18. A process according to  claim 17 , characterised in that the adhesive is a water soluble adhesive. 
     
     
       19. A process according to  claim 17 , characterised in that the adhesive is a cellulose ether. 
     
     
       20. A process according to  claim 17 , characterised in that the adhesive is methyl cellulose used as an aqueous solution. 
     
     
       21. A process according to  claim 17 , characterised in that the adhesive is polyvinyl pyrrolidone. 
     
     
       22. A process according to  claim 1 , characterised in that the adsorbent surfaces of the porous particles impart a selective filtration capacity for smoke constituents to the crimped tow.